Hemodialysis, hereinafter referred to as kidney dialysis, or simply “dialysis,” is a medical procedure that is performed on target subjects, for example humans, (and also, on a smaller scale, pet animals), to remove accumulated waste and toxins from the blood in a similar manner to a functioning kidney. When a person or animal's kidneys cease to function properly due to one or more of a number of acute or chronic diseases or conditions (e.g., diabetes, glomerulonephritis and hypertension are commonly recognized medical conditions that are associated with the development of renal failure), toxins accumulate in the bloodstream.
Failure to remove such accumulated waste and toxic compounds—primarily urea, uric acid and its analogues, and other nitrogenous compounds such as creatinine; and excess amounts of elements such as potassium, phosphorous, sodium, chloride and other minerals from the blood results in deterioration of body tissues and organ systems, which eventually results in death if untreated. Moreover, failure to remove such waste and toxins may result in uremia, which is a clinical syndrome that in many aspects resembles systemic poisoning. Almost every organ system in the body is affected by uremic toxicity and the known uremic clinical symptoms and side effects include, but are not limited to, fatigue, anemia, itching, peripheral neuropathy, gastrointestinal disorders including nausea, vomiting, diarrhea, cardiovascular complications including accelerated coronary and peripheral vascular disease, left ventricular hypertrophy, cardiac fibrosis and accelerated rates of arrhythmias. Conventional hemodialysis is capable of treating uremic symptoms that arise from “water soluble” non-hydrophobic uremic toxins, but dialysis is very ineffective in treating symptoms that arise from hydrophobic, protein-bound uremic toxins.
Generally, dialysis interposes a semi-permeable membrane between a flowing stream of blood and an appropriate rinsing solution. By convective and diffusive transport, the composition of body fluids approaches that of the dialysis solution. Dialysis may be performed in a hospital setting or clinic; or in some cases, the target subject is trained to perform the procedure at home on an outpatient basis. Two primary types of dialysis are regularly performed—conventional hemodialysis and peritoneal dialysis. In conventional hemodialysis, the target subject is connected (via an arteriovenous fistula, graft or by catheter) to a dialysis machine. The dialysis machine functions to pump the contaminated blood from the target subject through a dialyzer, where the blood is filtered through a dialyzing solution, thereby lowering the concentration of accumulated waste (e.g., urea), and thence returned to the target subject. Current dialysis membranes and technology are capable of clearing water soluble uremic toxins, but exhibit limited clearance of non-polar, hydrophobic, or protein bound toxins.
For example, p-cresol is an organic compound with the formula CH3C6H4(OH). It is a colourless solid that is a derivative of phenol and an isomer of o-cresol and m-cresol. A limitation of current dialysis treatment is the inability to remove all toxins from the bloodstream during a dialysis procedure. In particular, small hydrophobic compounds such as p-cresol, are known to build up and have the potential to cause severe toxicity. Current dialysis membranes and technologies are able to clear water soluble uremic toxins, but have limited clearance of non-polar protein bound toxins. Non-polar uremic toxins include, but are not limited to, p-cresol, p-cresol sulfate, and indoxyl sulfate. Thus, many target subjects, including patients undergoing kidney dialysis procedures, especially target subjects with advanced kidney disease have an accumulation of p-cresol in the plasma.
Further, p-cresol is derived from phenylalanine metabolism and has one of the highest plasma level of any known non-polar uremic toxins. Moreover, p-cresol, indoxyl sulfate and other protein bound uremic toxins have been linked to the development of vasculopathy, left ventricular hypertrophy, cardiac fibrosis as well as atrial and ventricular arrhythmias.
Accordingly, what is needed is a method and/or an apparatus that may be used during a dialysis procedure to remove hydrophobic, non-polar uremic toxins, such as p-cresol, from the blood.